Telephone-exchangee system



c. w. KECKLER..

TELEPHONE EXCHANGE SYSTEMv APPLICATION FILED SEPT-22. I916- 1,324,355. Patented Dem-9,1919;

2 SHEETS-SHEET I.

1 In van for: 0 i"! Char/es W. Keck/er. 7 by W Affy.

UNITED STATES rn'rnn rnrcn CHARLES W. KECKLER, O1" NEWARK, NEW' JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. 1., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Dec. 9, rate.

Application filed September 22, 1916. Serial No. 121,570.

Newark, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone-EX- change Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to such systems of the'central energy type in which telephone lines terminating at the same or different telephone exchanges may be interconnected by means of link or con necting circuits.

The object of this invention is the production of such a system by means of which the work of establishing connections between telephone lines may be greatly simplified.

In accordance with one feature of this invention, a link circuit employed in'establishing connections between telephone lines has associated therewith apparatus, controlled by the connection of the answering end of the link circuit with a telephone line or by a listening key cooperating with apparatus, operating upon the connection of the calling end with another line, to control the application of ringing current to the called telephone line.

In accordance with another feature of this invention, apparatus asociatedwith a connecting circuit prevents the connection of an operators telephone set with the talking strands thereof while the telephone'lines are joined thereby for conversation, but which permits such connection after the party on one of the lines has made a recall.

In accordancewith still another feature of this invention, apparatus associated with.

following description taken in connection with the drawings, wherein:

Figure 1 shows a telephone line and a cord circuit, the latter embodying certain features of this invention; and

Fig. 2 shows a trunk circuit and a telephone line, the former operating with the cord circuit shown in Fig. l and embodying certain other features of this invention.

Referring to the drawings, there are shown two telephone lines A and B, the former terminating at one central oilice, and the latter at a second central oi'lice. At the first central office there is a cord circuit C used for interconnecting telephone lines similar to A and B, it being understood that a plurality of such lines terminate at the first central voihce. This cord circuit C may also be used to connect a telephone line such as A with a trunk circuit D extending from the first to the second central oilice, the trunk circuit Dbeingadapted to connect at its other end with another telephone line, such as B.

Assuming that subscriber A. wishes to converse with subscriberB, A removes the receiver from the switchl'ioolr causing the operation of line relay 5 over a circuit from battery, through the winding oi line relay 5, right-hand windingof cut'ofi' relay 6, normal contact .thereoi, out over As line, through theiapparatus at the station, back over the other line, and through the lefthand winding of cut-oil relay 6 to ground. Line relay 5, in operating, causes line lamp 7 to light. Cut-oil relay 6, however, is diffcrentially wound so that it does not operate upon the completion or the circuit above traced. The operator observing the lighted condition of line lamp 7 inserts the answering plug of cord circuit G into the jack associated with As line, thereby causing the operation of relay 8 and cutoff relay (3 over a circuit from battery, through winding of relay 8, tip conductors of the answering plug and jack and the left-hand wind ing of cut-oil relay 6 to ground. Cut-off :rela 6 in oieratin connects the sleeve oi the jack with the ring thereof and causes the line lamp 7 to be extinguished. Relay 8, in operating, causes the operation of relay 9 over a circuit from battery, through the right-hand contact of relay 8, normal con.- tact oi. relay 10, normal contact and winding of relay 9, and lower norinal contact of relay 11 to ground. Relay 9, in operating, completes a locking circuit for itself by way of its left-hand alternate contact. Relay 12 now operates over a circuit which may be traced from battery, through the right-hand contact of relay 8, winding of relay 12, ring contacts of the plug and jack, over one side of the line, through the station apparatus,bacl-: over the other side of the line, and the left-hand windin of cut-oil relay 6 to ground. :lelay 12, in operating, causes the operation of relay 10 thereby preventing the lighting of the answering supervisory lamp l8. Relay 12, in operating, also causes the operation of a slowrelease relay 1st.

The operator may now actuate listeninglcey 20, thereby causing tle operation of relay 11 over a circuit from battery, through the winding of relay 11, upper contact of listening-key 20, middle alternate contact of relay 9 or normal contact. of relay 32 to ground. Relay 11, in operating, connects an operators telephone set to the talking strands of the cord circuit C, completes a locking circuit for itself through its lower alternate contact and releases relay 9. In this connection it is to be noted that if lis toning-key 20 is not actuated before the operation of relay 10, the answering supervisory lamp 13 will be lighted intermittently over a circuit from battery, through interrupter 21, right-hand alternate contact of relay 9, alternate contact of relay 10 and lamp 13 to ground. If this supervisory lamp is flashing when the listening-key s actuated, the release of relay 9 discontinues the flashing of the lamp because the right hand alternate contact of relay 9 is now open.

The operator, finding that subscriber B, whose line terminates at another central oflice, is desired, communicates with the operator at the second central office by means of an order wire circuit (not shown) and receives a trunk assignment. Assuming that the trunk circuit D has been assigned, the operator restores listening lrey 20 to normal position, releasing relay I1, and inserts the calling plug of cord circuit G into the jack of trunk circuit D, thereby causing the operation of relays and 21; over a circuit from battery, through the windings of relays 27 and 25, the lower normal contact of relay 28, upper normal contact of relay 1'1, tip contacts of the calling plug and jack, and the winding of relay 26 to ground. Relay 27 is marginal and does not operate when the calling plug is connected with the jack of a trunk circuit, but does operate when connected with the jack of a telephone line similar to A and P. Relay 25, in operating, causes the lighting of calling supervisory lamp 36 over a circuit from battery, through the lower alternate contact of relay 25, lamp 36 and conact of relay 52 to ground. This lamp remains lighted until B removes the receiver from the switchhook. Relay 26, in

contact of relay 12, left-hand alternate con-.

tact of relay 1%, winding of relay 32, upper normal contact of relay 28, ring contacts of the calling plug and jack, a winding of repeating coil 33, both windings of relay 30, another winding of repeating coil 33, winding of relay 31 and the contact of relay 29 to ground. The two windings of relay 30 are of high resistance preferably, pproximately 712,000 ohms, so that relay 32, which is marginal, does not operate when in series with both windings of relay 30, but does operate when one winding of relay 30 is short-circuited as will hereinafter more. fully appear. The operation of relay causes the lighting of lamp g-lover a circuit from batter through the alternate contact of relay 30, lower normal contact of relay 35, lamp 3% and the normal contact of relay to ground. v

The operator at the second central oliice, before whom. the lamp 34- is located, observes the lighted condition thereof and knows that the operator at the other central oliice has connected with the right trunk circuit, and tests line B. Assuming Bs line to be busy, there will exist at the sleeve contacts'of the jacks, a potential resulting from the connection of the sleeve contacts of one of the jacks with the live pole of battery, either by way of he calling or answering plug of a cord circuit or by way of the plug of a trunk circuit. This potential will be sufliciently above that of the point 1 2 between resistances and 70, so that upon the engagement of thetip of the plug of the trunk circuit with the sleeve contact of the aclncurrent will "low from the sleeve contact of the jack, through the tip of the plug, right-hand winding of relay 4-2, normal contact of relay -17, winding of polarized relays ll and 46, and resistance to ground. Relays ll and 4:6 are oppositely poled, and relay lS operates when its winding is traversed by current flowing in the direction just traced. Relay 46, in operating, close-s its contact connecting battery in circuit with a "winding 71 of an induction coil in the operators telephone set, whereupon a click'is heard in the operators receiver.

If line B is not busy, the operator inserts the plug of the trunk circuit D into the jack of Bs line, thereby causing the operation of polarized relay ll, relay 42, and cut-elf relay l3 over a circuit from battery, through contacted (which is located in the operators Jack and is closed whenever the operators plug is in the jack), resistance 45,. windings of polarized relays 46 and 41 (these relays are poled oppositely), normal contact of slow-release relay 47, right-hand winding of ing, causes the operation of slow-release relay 43 over a circuit from battery, through the contact of polarized relay 41, upper normalcontact of relay 35, contact of relay 42' and the winding of relay 48 to ground. Helay 48, in operating, causes the operation of relay 35 and slow-release relay 47 over a circuit from battery, through the contact of relay 48, winding of relay 35, left-hand contact of relay 49, contact of relay 55, and the winding of slow-release relay 4? to ground. The operation of relay 35 establishes. a looking circuit for relay 42 which may be traced from battery, through the upper alternate contact of relay .35, left-hand winding of relay 42, tip contacts of the plug and jack,

and right-hand winding of cut-ofirelay 43 to ground. Relays 35, 47 and 48 are now locked up under control 01 relay 42. Upon the operation of relay 35 lamp 34 is extinguished, and relay56 and slow-release relay 40 operate over a circuit from battery, through the alternate contact of relay 30,

lower alternate contact of relay 35, and the windings of relays 40 and 56 in parallel to round. The 0 ration oi slow-release re- 23 lay 40 prepares a circuit for the right hand winding of relay. 49. Relay 56, in operating, connects a source of ringing current 57 to Bs line. The circuit therefor may be traced from source 57, through the Winding of tripping relay 55, upper alternate contact of relay 56, ring contacts of the plug and jack, out over one side of the line, through the call bell at station B, back over the other side of line, tip-contacts ot the jack and plug, lower alternate contact of relay 56, re

sistance 58, through battery to ground.-. Sub.

scriber B, in responding to the operation of the call lbell, removes the'receiver irom the switchhook and causes the operation of relay 55 which opens a short circuit through the left-hand winding of relay 49, which thereupon operates and opens the circuit of relay 56, which releases and disconnects ringing current from Bs line. Relay 49, in operat ing, is locked up in circuit with relays 35 and 47. Upon the release of relay 56, relay 59 operates .over the line circuit, and, in operating, short-circuits theupper winding of relay 30, thereby permitting the opera-= tion of marginalrelay 32. M Marginal relay in operating,extinguishes the calling su pervisory lamp 36 in the cord circuit C After the completion of theconversation between subscribers A and B, both restore the receivers to the switchhooks, the restoration of the receiver at stationjA causing the release of relay 12, and in turn, relays 10 and 14. Upon the release of relay 10, an swering supervisory lamp 13 is lighted to furnish a disconnect signal. Restoration of the receiver to the switchhook at station B causes the release'of relay 59 which opens the'short circuitof the upper winding of relay 30, thereby causing the release of marginal relay 32 whereupon the calling supervisory lamp 36 is lighted to furnish a dis connect signal. The operator at the first central ofiice, observing the lighted condition of the disconnect signals 13 and 36,

withdraws the answering and calling plugs from the jacks whereupon relay 30 in the trunk circuit D releases, and, in releasing, causes the release of relay 40, whereupon the lamp 34 is lighted over a circuit from battery, through the normal contact of relay 30, right-hand contact of relay 47, lamp 34 and normal contact of relay 40 to ground. The operator at the second central ofiice, observing the lighted condition of the dis connect lamp 34, withdraws the plug of the trunk from the jack of He line, whereupon all apparatus associated with both lines, the cord circuit and the trunk circuit is returned to normal condition.

It will be assumed that subscriber A has called for subscriber B, that the cords circuit connects line A with the trunk circuit D, that the plug of trunk circuit D is connected with the jack of Bs line, and that the call bell at subscriber Bs station is being operated. Now suppose that before subscriber B responds, subscriber A abandons the call, in which case the restoration to the switchhook of the receiver by subscriber A causes the release of relay 12, thereby re leasing relays 10 and 14, and lights the answering supervisory lamp 13. The release of relay .10 causes the operation of relay 9 over a circuit hereinbefore traced. During the time-between the release of relay 12 and therelease of slow-release relay 14, current is removed from the circuit including relays 30, 31 and 32.- Relays 30 and 31 thereupon release momentarily or until slow-release relay 14 has completely released, whereupon the circuit including the relays 30, 31. and 32 is again established. Upon the momentary release of relay 30, relay 49 is operated over a circuit from battery, through the normal contact of relay 30, right-hand winding of relay 49, and alternate contact of slow-release relay lO to ground. Relay 49, in operating,causes the release of relay 56 in the manner described in connection with the tripping of the ringing by the response of subscriber B. Relay 49, in operating, is locked up in circuit with relays 35 and 47 as before described. Relay 40 is, as before described, of the slow-releasing type, and is so made that it will not release, due to the momentary release of relay 30 and furnish a disconnect signal by the lighting of lamp 3-1. Lamp 3t is not lighted at this time because the relay 4C0 fails to release, before the relay 30 is again energized upon the complete release of relay 1 1.

Should subscriber A, upon completion of the conversation, wish to attract the attention of the operator at the first central office to make a recall or for any other purpose, restoration of the receiver to the switchhook, followed by the removal therefrom before the cord circuit C is disconnected from As line, will cause the answering supervisory lamp 13 to be lighted intermittently to furnish a recall signal. This is accomplished in the following manner: Upon the restoration of the receiver at station A to the switchhook, relays 12, 10 and 14. release, and upon the release of relay 10, relay 9 operates and completes a locking circuit for itself as hereinbefore described. The subsequent energization of relay 12,. followed by the energization of relay 10, due to the removal of the receiver from the switchhook at station A,'includes the interrupter 21 in circuit with the lamp 13 and battery, whereupon the lamp is lighted in termittently. The operator at the first central oiiice, observing the flashing of the supervisory lamp 13, may actuate listening key 20, ther by causing the operation of relay 11, which, in operating, locks up and causes the release of relay 9 to stopthe flashing of the supervisory lamp 13. The operator may now complete any desired connection for subscriber A.

It will now be assumed that subscriber A desired to be connected with a line terminating in the same central office. This line is similar in all respects to lines A and B, and in the following description it will be supposed, for the sake of convenience, that line B terminates in the first central office. The operator, after inserting the answering plug of cord circuit G into the jack of line A and having been advised by subscriber A that connection is desired with a line terminating in the same central ollice, for example, line B, restores listening-key 20' to normal position, releasing relay 11 and .insorts the calling plug of the cord circuit G into the jack of Bs line, whereupon relays 27, 25 and l3 are operated over a circuit from battery, through the windings of relays 27 and 25, lower normal contact of relay 28, upper normal contact of relay 11, tip contacts of the plug and jaclgand the right-hand winding of cut-off relay l3 to ground. The relay 25, in operating, lights the calling supervisory lamp 36. The op eration of relay 27 causes the operation of relay 28 over a circuit from battery through the contact of relay 27, winding of relay 28, contacts of relay 60 and 61, left-hand contact of relay 8 and resistance 62 to ground. Relay 28,in operating, completes a temporary locking circuit for relays 27 a and 25 by way of the middle alternate contact of relay 28 and resistance 68 to ground. The'opening ofthe lower normal contact of relay 28 upon itsoperation thereby disconnects battery and relays 27 and 25 from the tip strands, and substitutes therefor battery through resistance 6 1, to prevent the possibility of the release of these relays due to ringing current, as will hereinafter more fully appear. Relay 28, in operating, also connects a source of ringing current to Bs line through the winding of tripping relay 61, upper alternate contact of relay 28, ring contacts of the plug and jack, out over the one side of the line, through the call bell of station E, back over the other side of the line, tip contacts of the jack and plug, upper normal contact of relay 11', and alternate contact of relay 25 in parallel, lower alternate contact of relay 28 and resistance 64 through battery to ground. Subscriber B, in responding by the removal of the receiver from the switchhook, causes the operation of relay 61, which, in operating, removes the short-circuit from the lefthand winding of relay 60. Relay 60 now operates over a circuit from battery, through the contact of relay 27, winding of relay 28, left-hand winding of relay 60, left-hand contact of relay 8 and resistance 62 to ground. Relay 60, in operating, completes a locking circuit for itself from battery,

through the lower alternate contact of relay 25, alternate contact of relay 60, lefthand winding thereof, left-hand contact of relay 8 and resistance 62 to ground, and establishes shortcircuit for relay 28 which thereupon releases, disconnecting the ringing current from the line and again connecting battery to the tip strand of the cord circuit through the windings of relays 27 and 25. Relay 32 now operates over a cir cuit from battery through the alternate con tact of relay 12, left-hand alternate contact of relay 14L, winding of relay 32, upper normal contact of relay 28, ring contacts of the plug and jack, out over one side of the line, through the station apparatus, back over the other side of line, and the righthand winding of eut-o-fl relay 43 to ground. The operation ofrelay 32 extingnishes calling supervisory lamp 3-6. At the completion of conversation, subscribers A and B restore the receivers to the switchhooks. causing the release of relays 12, 10, ljl and 32, whereupon circuitsare completed for the answering and calling supervisory lamps 13 and 36 which are thereby lighted to furnish disconnect signals. The operator may now withdraw the plugs from the jacks, whereupon all apparatus is returned to normal.

If, forany reason, the operator at the first central oflice should wish to'originate a calling plug of the cord circuit G into the jack of As line, whereupon relays 27 25 and cut-off relay 6 operate over a circuit from battery, windings of relays 27 and 25,

lower normal contact of relay 28, upper normal contact of relayll, tip. contacts of the calling plug and jack, and the left-hand winding of cut-ofi relay 6 to ground. By the operation of relay 25 the upper alternate contact thereof is closed, completing a look ing circuit for relays 27, 25 and 6, so that the subsequent operation of relay 11 will have no effect upon these three relays. Relay 27, in operating, closes a contact in circuit with relay 28, but this relay 28' does not operate, for the circuit is not. complete, it being open at the left-hand contact of relay 8, and at the lower contact of the listenin key 20 (which contacts are in parallel Since the answering end of cord circuit C is not connected with a line, relay 28 cannot operate until the listening-key 20 is actuated. Upon the actuation of the listeningkey, relay 28 operates over a circuit from battery, through the contact of relay 27, winding of relay 28, normal contacts of relays and 61, lower contact of listeningkey 20, and resistance 62 to ground. Upon the operation of relay 28, ringing current is connected to As line- Before the response of subscriber A, should the operator, for, any reason, desire to discontinue ringing on this line, the restoration of the listeningkey 20 to normal will bring about such a result. In this way the operator may employ a machine ringing cord circuit to originate a call on any line, and after ringing thereon may discontinue such ringing and still hold the line sothat upon the response of the signaled party, the calling supervisory lamp will be extinguished. This scheme permits the operator to signal the party, and while waiting for the response thereof, attend to the answering and com pleting of other calls.

What is claimed is: p

1. A telephone exchange system comprising subscribers lines, a'link circuitconnecting the lines, an operators telephone set normally disconnected from the link circuit, a listening relay controlling the connection of the operators telephone set to the link circuit, a second relay associated with the link circuit, an operating circuit for the second relay including a contact on the listening relay completed upon the restoration of the receiver to theswitchhook at one of V the connected stations, operator-controlled switching means, and an operating circuit for the listening relay jointly controlled by the second relay and the operator-controlled switching means.

2. A telephone exchange system compris ing subscribers lines, a link circuit connecting the lines, an operators telephone set normally disconnected from the link circuit, a listening relay for connecting the operators telephone set to the link circuit, a sec ond relay associated with the link circuit, an operating circuit including a Contact of the listening relay completed upon the opening of the line circuit at the calling station, a manually operated switch, and an operating circuit for the listening relay closed by the energization of the second relay and the actuation of the switch.

3. A telephone exchange system comprising subscribers lines, a link circuit connecting the lines, an operators telephone set normally disconnected from the link circuit, a listening relay for connecting the op erators telephone set to the link circuit, a supervisory relay associated with the answering end of the link circuit, a third relay, an operating circuit therefor including a contact of the listening relay completed upon the deenergization of the supervisory relay, a manually operated switch, and an operating circuit for the listening relay closed by the energization of the third relay and the actuation of the switch.

4:. A telephone exchange system comprising telephone lines, a link circuit, an operators telephone set, a listening key controlling the connection of the operators telephone set to the link circuit, a source of ringing current, a relay for connecting said source to a line, and an operating circuit for said relay controlled jointly by said listening key and the connection of said link circuit with a line independent of the conpection of the link circuit with any other 5. A telephone exchange system compris ing telephone lines, a link circuit, a source of ringing current, a relay for connecting said source to a line, and an operating circuit for said relay jointly controlled by the connection of the ends of the link circuit with telephone lines, independent of the condition of the substation apparatus associated with said lines.

6. A telephone exchange system comprising telephone lines, a link circuit, an operators telephone set, a listening key controlling the connection of the operators telephone set to the link circuit, a source of ringing current, and a relay for connecting said source to a called line jointly controlled by the connection of the answering end of the link circuit with a line or the actuation of the listening key and the connection of the calling end of the link circuit with the called line.

7 A telephone exchange system comprisin a telephone line terminating in a plura ity of sets of terminals, a test terminal for each set normally free "from battery and ground connections, a connecting circuit, a cut-off relay for each line actuated upon connection of the connecting circuit with a set of the terminals to connect a source of potential to the test terminals, :1, second connecting circuit, an operators receiver, and at polarized relay responsive to the engagement of the second connecting circuit with at test terniinel of a busy line, and, a circuit completed by the operation of the polarized 10 relay to produce a click 1n the operators receiver.

In Witness whereof, I hereunto subscribe my nznne this 19th day of September, A. D.

CHARLES WV. KE GKLER. 

